Substructure in Tidal Streams; Tributaries in the Anticenter Ring

We report on the detection in Sloan Digital Sky Survey data of at least three, roughly parallel components in a 65 degree-long stellar stream complex previously identified with the Anticenter or Monoceros Ring. The three-stream complex varies in width from 4 to 6 degrees along its length and appears to be made up of two or more narrow substreams as well as a broader, diffuse component. The width and complexity of the stream indicate that the progenitor was likely a dwarf galaxy of significant size and mass. The stream is 8.9 kpc distant and is oriented almost perpendicularly to our line of sight. The visible portion of the stream does not pass near any known dwarf galaxies and a preliminary orbit does not point to any viable progenitor candidates. Orbits for the narrower substreams can be modeled with velocity offsets from the broad component of about 8 km/s. We suggest that the broad component is likely to be the remains of a dwarf galaxy, while the narrower streams constitute the remnants of dynamically distinct components which may have included a native population of globular clusters. While the color of the main sequence turn-off is not unlike that for the Monoceros Ring, neither the visible stream nor any reasonable projection of its orbit passes through Monoceros or Canis Major, and we conclude that this stream is probably unrelated to the overdensities found in these regions.Comment: 11 pages, 4 figures, accepted for publication in ApJ Letter

KC-135 aero-optical turbulent boundary layer/shear layer experiment revisited

The aero-optical effects associated with propagating a laser beam through both an aircraft turbulent boundary layer and artificially generated shear layers are examined. The data present comparisons from observed optical performance with those inferred from aerodynamic measurements of unsteady density and correlation lengths within the same random flow fields. Using optical instrumentation with tens of microsecond temporal resolution through a finite aperture, optical performance degradation was determined and contrasted with the infinite aperture time averaged aerodynamic measurement. In addition, the optical data were artificially clipped to compare to theoretical scaling calculations. Optical instrumentation consisted of a custom Q switched Nd:Yag double pulsed laser, and a holographic camera which recorded the random flow field in a double pass, double pulse mode. Aerodynamic parameters were measured using hot film anemometer probes and a five hole pressure probe. Each technique is described with its associated theoretical basis for comparison. The effects of finite aperture and spatial and temporal frequencies of the random flow are considered

Extended range harmonic filter

Two types of filters, leaky-wall and open-guide, are combined into single component. Combination gives 10 db or greater additional attenuation to fourth and higher harmonics, at expense of increasing loss of fundamental frequency by perhaps 0.05 to 0.08 db. Filter is applicable to all high power microwave transmitters, but is especially desirable for satellite transmitters

Spin transport in coupled spinor Bose gases

We report direct measurements of spin transport in a trapped, partially condensed spinor Bose gas. Detailed analyses of spin flux in this out-of-equilibrium quantum gas are performed by monitoring the flow of atoms in different hyperfine spin states. The main mechanisms for motion in this system are exchange scattering and potential energy inhomogeneity, which lead to spin waves in the normal component and domain formation in the condensate. We find a large discrepancy in domain formation timescales with those predicted by potential-driven formation, indicating strong coupling of the condensate to the normal component spin wave

Response of Saddled Prominent (Lepidoptera: Notodontidae) Pupae to Desiccation, Cold Treatment, and Post-Cold Treatment Incubation Temperature

Saddled prominent, Heterocampa guttivitta, pupae were placed at 1.5oC for 50 to 200 days, then incubated at one of four post-cold temperatures ranging from 10° to 26.7°C. Adults emerged from pupae exposed to all cold treatment periods. A few adults also emerged from pupae that were not exposed to cold. The time required for adult emergence following cold treatment declined with longer periods of cold treatment and higher post-cold incubation temperature. The interaction between these two main effects was also significant. Adult morphogenesis begins immediately after pupation, and continues until interrupted by cold temperature. When pupae were subjected to desiccating conditions prior to cold treatment, weight loss due to desiccation was accompanied by increased mortality. Desiccation occurred faster at IS.6° than at 18.0°C. Our results identify a physical factor which might contribute to pupal overwintering mortality: prolonged excessive drought conditions between time of pupation and the onset of cold

Evolution: Complexity, uncertainty and innovation

Complexity science provides a general mathematical basis for evolutionary thinking. It makes us face the inherent, irreducible nature of uncertainty and the limits to knowledge and prediction. Complex, evolutionary systems work on the basis of on-going, continuous internal processes of exploration, experimentation and innovation at their underlying levels. This is acted upon by the level above, leading to a selection process on the lower levels and a probing of the stability of the level above. This could either be an organizational level above, or the potential market place. Models aimed at predicting system behaviour therefore consist of assumptions of constraints on the micro-level – and because of inertia or conformity may be approximately true for some unspecified time. However, systems without strong mechanisms of repression and conformity will evolve, innovate and change, creating new emergent structures, capabilities and characteristics. Systems with no individual freedom at their lower levels will have predictable behaviour in the short term – but will not survive in the long term. Creative, innovative, evolving systems, on the other hand, will more probably survive over longer times, but will not have predictable characteristics or behaviour. These minimal mechanisms are all that are required to explain (though not predict) the co-evolutionary processes occurring in markets, organizations, and indeed in emergent, evolutionary communities of practice. Some examples will be presented briefly

Non-equilibrium dynamics of an active colloidal "chucker"

We report Monte Carlo simulations of the dynamics of a "chucker": a colloidal particle which emits smaller solute particles from its surface, isotropically and at a constant rate k_c. We find that the diffusion constant of the chucker increases for small k_c, as recently predicted theoretically. At large k_c the chucker diffuses more slowly due to crowding effects. We compare our simulation results to those of a "point particle" Langevin dynamics scheme in which the solute concentration field is calculated analytically, and in which hydrodynamic effects can be included albeit in an approximate way. By simulating the dragging of a chucker, we obtain an estimate of its apparent mobility coefficient which violates the fluctuation-dissipation theorem. We also characterise the probability density profile for a chucker which sediments onto a surface which either repels or absorbs the solute particles, and find that the steady state distributions are very different in the two cases. Our simulations are inspired by the biological example of exopolysaccharide-producing bacteria, as well as by recent experimental, simulation and theoretical work on phoretic colloidal "swimmers".Comment: re-submission after referee's comment